Electromagnetic driving mechanism



June 1970 TSUNETA KAWAKAMI ETAL 3,513,454

ELECTROMAGNETIC DRIVING MECHANISM Filed Dec. 24, 1968 s Sheets-Sheet 1June 30, TSUNETA KAWAKAN ETAL v ELECTROMAGNETIC DRIVING MECHANISM 5Sheets-Sheet Filed Dec. 24, 1968 m N ll m H M J Q llliAl'll llllr T I!|..l L n Q |||L u w 9 June 30,1970 TSUNETA KAWAKAMI ETA!- 3,513,464

ELECTROMAGNETIC DRIVING MECHANISM 5 Sheets-Sheet 5 Filed Dec. 24, 1968 mUNLN TORQUE June 30, 1970 1 TSUNETA KAWAKAMI E 3,

ELECTROMAGNETIC DRIVING MECHANISM Filed Dec. 24, 1968 5 Sheets-Sheet 4FIG. 6'

DISPLACEMENT OF MAGNETIC POLE WITH/N I CYCLE June 30, 1970 TSUNETAKAWAKAMI ErAL 3,518,464

ELECTROMAGNETIC DRIVING MECHANISM Filed Dec. 24, 1968 5 SheetsSheet 5United States Patent 3,518,464 ELECTROMAGNETIC DRIVING MECHANISM TsunetaKawakami, Chiha-shi, Hitoshi Ikeno, Tokyo, and

Masami Sato, Matsudo-shi, Japan, assignors to Kabushiki Kaisha HattoriTokeiten Filed Dec. 24, 1968, Ser. No. 786,620 Claims priority,application Japan, Dec. 30, 1967,

Int. Cl. H02k 7/06 U.S. Cl. 310-22 11 Claims ABSTRACT OF THE DISCLOSUREMagnetic driving mechanism comprises a driven wheel, a magnetic poleunit having at least three spaced magnetic poles, and exciting means tooscillate said magnetic pole unit whereby said driven wheel is rotatedunidirectionally in a self-starting manner.

BACKGROUND OF THE INVENTION Field of the invention The present inventionrelates to magnetic driving mechanism of the self-starting type adaptedto be generally used in clocks or watches.

Description on prior art Known magnetic driving mechanisms of theselfstarting type generally comprises a rotating wheel made of amagnetic substance and provided with circumferentially spaced teeth eachhaving a tooth profile asymmetric with respect to the radial directionof said rotating wheel, and an oscillating element provided with amagnetic pole acting magnetically on the teeth upon the oscillatingelement being excited, so as to rot-ate the rotating wheel in aself-starting manner. However, as the teeth of the rotating wheelinvolve an extremely complicated tooth profile and require highprecision which cannot be obtained by usual press works, none hasheretofore come into commercial use. Further, employment of such priormagnetic driving mechanism as an escapement mechanism has a tendency toadverse effects on the frequency of the oscillating element, caused bythe asymmetric tooth profile. It will thus be apparent that anescapement mechanism of this type is lacking in isochronism.

TECHNICAL SUBJECT-MATTER OF THE INVENTION It is an object of the presentinvention to eliminate the above-mentioned shortcomings in the priormagnetic driving mechanism and to provide a novel and improved magneticdriving mechanism.

In accordance with a feature of the present invention, there is providedmagnetic driving mechanism comprising a driven wheel having at aperipheral part thereof a magnetically neutral circle, and magneticdriven parts arranged on opposite sides of said magnetically neutralcircle in an alternately staggered relation to each other; at least onemagnetic pole driving unit having at least three magnetic poles locatedin opposed relation to said magnetic driven parts; and exciting means tooscillate said magnetic pole driving unit in a direction across saidmagnetically neutral circle, the sum total of rotating energy exerted onsaid magnetic driven par-ts by magnetic attractive forces of saidmagnetic pole driving unit at the time when said magnetic pole drivingunit is offset toward one of its alternative amplitude positions beinglarger in magnitude than the sum total of rotating energy exerted onsaid magnetic driven par-ts by magnetic 3,518,464 Patented June 30, 1970ice attractive forces of said magnetic pole driving unit at the timewhen said magnetic pole driving unit is offset toward the otheramplitude position, and further the former rotating energy and thelatter rotating energy acting in opposite directions to each other atleast at the time when said driven wheel starts to rotate. Thus, themagnetic pole units made an oscillatory movement under a condition inwhich the driven wheel is within a magnetically stable angular zone. Inan initial stage when the oscillatory movement of the magnetic pole unitis still small in amplitude, the driven wheel will make a rotationaldisplacement alternately in opposite directions. On the other hand, in astage when the oscillatory movement of the magnetic pole unit becomescomparatively larger in amplitude, the driven wheel may be rotated intoa new and adjoining magnetically stable zone by the larger rotatingenergy. The driven wheel is naturally subjected to external loads ofvarious types and, therefore, the driven wheel upon its movement into anew stable zone may follow the magnetic poles with an inevitable phaselag with respect to the latter. As a result of such phase lag, thedriven wheel, after having moved into saidadjoining stable zone, is notkept in said zone but is rotated afresh in the same direction by thesucceeding oscillation of the magnetic pole units so that the drivenwheel may start to rotate in a fixed direction in a self-startingmanner. Once the driven wheel starts rotating, it may continue itssteady and unidirectional rotation due to said larger rotating energywhich acts on the driven wheel in the rotating direction of the latter.

To obtain the elfects in which the sum of rotating energy at the timewhen said magnetic pole unit is offset toward one of its alternativeamplitude positions is larger in magnitude than the sum total ofrotating energy at the time when said magnetic pole unit is olfsettoward the other amplitude position, and further the former rotatingenergy and the latter rotating energy act in opposite direction to eachother, it may be preferred that at least one pitch provided between anyadjacent two of at least three magnetic poles is somewhat larger than aninteger times the pitch between any adjacent two parts .of said drivenparts, while another pitch provided between two adjacent magnetic polesis somewhat smaller than an integer times said pitch of said drivenparts.

Preferably, the driven wheel may be made from either a disc in which theinner and outer driven parts, each being symmetrical 'with respect tothe radial direction of the disc, are arranged in a continuously sinuousmanner, or a modified disc in which the inner and outer driven parts arearranged in discontinuous manner.

Furthermore, another modification of the driven wheel comprises a discof gear wheel type having therearound a plurality of circumferentiallyspaced first driven parts, and another disc of gear wheel type havingtherearound a plurality of circumferentially spaced second driven parts,the two discs being superposed one over another. The driven partsprovided in the driven wheel of this invention can be easily fabricatedby conventional press works.

An object of the present invention is the provision of magnetic drivingmechanism to steadily rotate the driven wheel in a fixed direction,which is easy to fabricate and moderate in price.

Further features, advantages and objects of the present invention willbecome apparent from the following description with reference to theaccompanying drawings.

BRIEF EXPLANATION OF THE DRAWING FIG. 1 is a plan view illustrating apreferred embodiment of magnetic driving mechanism according to thepresent invention;

FIG. 2v is a side view, with a part thereof broken away, of the magneticdriving mechanism of FIG. 1;

FIG. 3 is an enlarged perspective view showing a magnetic pole unit;

FIG. 4 is an enlarged diagrammatic view illustrating a positionalrelationship between the driven parts and the magnetic poles in theirstable positions;

FIG. 5 is a schematic illustrating sine wave forms which 'will assist inunderstanding the relative displacement of the magnetic poles to thedriven wheel;

FIG. 6 is a graph illustrating variation of the rotating torque througha complete cycle of the relative displacement shown in FIG. 5;

FIG. 7 is a side view illustrating a modified embodiment of the drivenwheel;

FIG. 8 is a side view showing another embodiment of the driven wheel;and

FIG. 9 is a side view illustrating still another embodiment of thedriven wheel.

DETAILED EXPLANATION OF PREFERRED EMBODIMENTS Reference will be now madeto FIGS. 1 to 3 showing a preferred embodiment which is provided withmagnetic pole units each having three magnetic poles. Oppositely spacedparallel base plates 1 support on their foremost extremities a traverseshaft 2 in a freely rotatable manner. Fixed on the shaft 2 is a drivenwheel 3. A damper disc 4 of brass is mounted for rotation on the shaft2. The base plates 1 are integral with each other at their rearmost endsthrough a connecting portion on which is mounted by screws 5 therearmost end of an oscillating spring element 6 extending tangentiallyof the driven wheel 3. Secured to the free or foremost end of theoscillating element 6 is a C-shaped permanent magnet 7 by means ofscrews 8. The magnet 7 includes oppositely spaced arms the forward endsof which are formed with a pair of oppositely facing magnetic poledriving units 9.

The driven wheel 3 comprises a disc, preferably made of magneticsubstance such as Permalloy which has high magnetic permeability. Thedisc of the driven wheel 3 comprises a magnetically neutral portion 20of annular configuration, magnetic outer driven parts 10 extendingradially of the disc and arranged around the outer periphery of theneutral portion 20 at a fixed circumferential pitch and separated bynotches 11 which are provided between adjacent outer driven parts, andmagnetic inner driven parts 12 extending radially of the disc andarranged along the inner periphery of the neutral portion 20 at a fixedcircumferential pitch with apertures 13 provided between adjacent innerdriven parts. The outer and inner driven parts 10 and 12 are ofrectangular contour symmetrical with respect to the radial direction ofthe driven wheel 3. Furthermore, the inner driven parts .12 are locatedbetween adjacent outer driven parts 10, that is to say, the inner drivenparts 12 are located in a staggered relation to the outer driven parts10. A magnetically neutral circle 14 is positioned substantially halfwayof the radial width of the annular neutral portion 20, as shown by adotted line in FIG. 2.

Referring now to FIG. 3, each of the magnetic pole driving units 9comprises three magnetic poles 15a, 15b and 15c of a rectangularconfiguration, said magnetic poles being disposed in parallel and spacedrelation to each other and also in opposed relation to said neutralcircle 14 of the driven wheel 3. The magnetic poles are, moreover,arranged in such a manner that a first pitch P provided between a firstpair of adjacent magnetic poles 15a and 15b is longer than a pitch Pmeasured along the neutral circle 14 between any adjacent outer drivenparts 10, and that a second pitch P provided between a second pair ofadjacent magnetic poles 15b and 15c is shorter than the above-mentionedpitch P. As an example,

assuming that the driven wheel has an outer diameter of 12. mm., aneutral circle diameter of 1011 mm., the pitch P measured along theneutral circle between and adjacent outer. driven parts 10 of 0.79 mm.and the number of outer driven parts is 40, the *first pitch P of themagnetic pole unit may be 0.87 mm. and the second pitch P may be 0.64mm. It should be noted that the magnetic poles 15a, 15b and are equal inwidth to the width of the outer driven parts 10.

Driving means for actuating the oscillating element 6 may be of theconventional type which comprises a cylindrical magnet core 16projecting upwardly from the upper surface of the forward end of saidoscillating element 6, and a hollow cylindrical coil 17 adapted toreceive the magnet core 16. The coil 17 is mounted on a holder 18 whichis fixed to the base plates 1.

Operation of the magnetic driving means constructed as described abovewill be hereinafter given in detail. In case where the oscillatingelement 6 is not yet actuated, the driven wheel 3 may be at a standstillin its magnetically stable position. Referring now to FIG. 4 showing oneof the magnetically stable positions in which the driven wheel 3 may beat a standstill, the centers 19a, 19b and of the magnetic poles 15a, 15band 15c are all located on the neutral circle 14 so that the resultantof magnetic attractive forces of the three magnetic poles 15a, 15b and150, applied to their associated three outer driven parts 10, and theresultant of magnetic attractive forces, applied to'their associatedthree inner driven parts 12, are equal in magnitude but acting inopposite directions to each other. As a result, the driven wheel 3 ismaintained at a standstill.

Secondly, suppose the oscillating element 6 starts to oscillate by meansof the coil 17 periodically excited by electric current, the oscillatingelement 6 will commence oscillating the magnetic pole units 9 in adirection radially of the driven wheel 3 across the neutral circle 14and also such oscillatory movement of the magnetic pole units 9 willgradually increase in amplitude. In an initial stage in which theoscillatory movement of the magnetic pole units is still small inamplitude, when the magnetic pole units are offset radially outwardlytoward their first amplitude position, the resultant of magneticattractive forces acting on the outer driven parts 10 is greater inmagnitude than the resultant of magnetic attractive forces acting on theinner driven parts 11 with the result that the driven wheel 3 may rotatein a counterclockwise direction (as viewed in FIG. 4) through a limitedangle. Subsequently, upon the magnetic pole units being offset radial-1y inwardly toward their alternative amplitude position, the resultantof magnetic attractive forces acting on the outer driven parts 10 isless in magnitude than the resultant of magnetic attractive forcesacting on the inner driven parts 12, whereby the driven wheel 3 mayconversely make a clockwise rotation through a limited angle. From theforegoing, it will be apparent that the driven wheel 3 is permitted torotate alternatively forwards and backwards within a limited angle. Suchalternative rotational displacement of the driven Wheel 3 in oppositedirections is defined within the angular range in which the driven wheel3 may be restored to its original, magnetically stable position, that isto say, within a magnetically stable angular zone, and moreover thedriven parts of the driven wheel 3 may follow the magnetic pole unitswith some phase lag with respect to the latter, because of loads due toinertia and bearing friction of the driven wheel or due to gear trainsintermeshed with the driven wheel.

In order to produce unidirectional rotational displacement of the drivenwheel, an important consideration is that the sum total of rotatingenergy applied to the outer driven parts 10 at the time when themagnetic pole units are oifset radially outwardly is larger in magnitudethan the sum total of energy applied to the inner driven parts 12 at thetime when the magnetic pole units are offset radially inwardly, wherebythe rotational displacement of the driven wheel 3 at the time when themagnetic pole units are offset radially outwardly is larger in angularamount than when the magnetic pole units are offset radially inwardly.Thus, it will be apparent that the rotational displacement of the drivenwheel will gradually increase in magnitude as the oscillatory movementof the magnetic pole units is gradually increased in amplitude, however,the rotational displacement of the driven wheel 3 beyond theabove-mentioned magnetically stable angular zone will necessarily occuronly when the magnetic pole units are offset radially outwardly. Thisforms the basis of the fact that the driven Wheel 3 may always, and withcertainty be made to rotate unidirectionally (the rotation al movementbeing in a counterclockwise direction in FIG. 4).

The driven wheel 3, after having thus gotten away from a magneticallystable angular zone, will move into a new and adjoining stable positionand at this time the driven parts of the driven wheel, rotated by virtueof the magnetic attractive forces of the magnetic poles, may follow themagnetic poles with somewhat of a phase lag with respect to the latterby the reason of the loads, as described above, applied to the drivenwheel. According- 1y, such phase lag causes the driven wheel to rotatecontinuously and unidirectionally whereby the driven wheel 3 is made torotate with a counter-clockwise rotational movement in a self-startingmanner. The damper disc 4 has for its object to smooth out therotational movement of the driven wheel.

Illustrated in FIG. 5, is a curve G showing the relative displacement ofthe center 19b of the intermediate magnetic pole 15b to the driven wheel3 which makes a steady rotation in a counter-clockwise direction,including the above-mentioned phase lag h. It will be seen that thecurve G is of substantially sine wave form. While the relativedisplacement in connection with the remaining magnetic poles 15a and 15cmay be also shown by sine wave forms substantially similar to said curveG, these additional sine wave forms are omitted in FIG. 5.

FIG. 6 is a graph showing variation of the resultant of rotating torquesexerted on the driven wheel 3 by the three magnetic poles 15a, 2151; and150 during a complete cycle period of the sine wave form G shown in FIG.5. In FIG. 6, a torque curve T indicates that almost all of the rotatingtoruqes are applied to the driven wheel 3 in the forward orcounter-clockwise direction, whereas the rotating torque exerted on thedriven wheel 3 in the backward or clockwise direction is small inmagnitude and also extremely short in period so that the driven wheel 3may take a steady and unidirectional rotation.

The question will arise as to what additional rotating torques would beexerted on the driven wheel 3 by the magnetic poles in the event thedriven wheel 3 is forcibly rotated in the backward or clockwisedirection owing to external force. A since wave form Ga in FIG. showsthe relative displacement of the center 19b of the magnetic pole 15b tothe driven wheel 3 at a time when the driven wheel 3 is forcibly causedto rotate in the backward or clockwise direction with a phase lag h.Variation of rotating torques exerted on the driven 'wheel 3 under suchbackward rotation is shown by a torque curve Ta in FIG. 6. It will beseen from this torque curve Ta that the energy applied to the drivenwheel 3 by the rotating torques in the backward or clockwise direction,even under the backward rotation of the driven wheel, is substantiallyequal in magnitude to the energy applied by the rotating torques in thenormal or counterclockwise direction, and therefore the driven wheel 3does not acquire a suflicient energy to continue the backward orclockwise rotation. As a result, if the external force is eliminated,the driven wheel 3 will be attenuated to a stop and will again start tomake its normal, counterclockwise rotation.

Alternative details of magnetic driving mechanism in accordance with theinvention will be hereinafter described by way of example. Assuming thatthe driven Wheel has an outer diameter of 12 mm., a neutral circlediameter of 10.1 mm. and 40 outer driven parts spaced circumferentiallyof the neutral circle with a pitch P of 0.79 mm. measured along theneutral circle between any adjacent driven parts, a magnetic pole unitmay be provided in which the first pitch P is 0.94 mm. and the secondpitch P is 0.71 mm.

Further, taking into consideration a modified magnetic pole unit inwhich the first pitch P exceeds twice the second pitch P in case wherethe driven wheel has an outer diameter of 12 mm., a neutral circlediameter of 10.1 mm. and 40 outer magnetic driven parts spacedcircumferentially of the neutral circle with a pitch P of 0.79 mm.measured along the neutral circle between any adjacent driven parts, amagnetic pole unit will be provided in which the first pitch P is0.79+0.94=l.73 mm. and the second pitch P is 0.71 mm.

FIG. 7 shows a modified driven wheel 103 which has a neutral portionreduced in its radial width as compared with that of FIG. 2. In thisfigure, components indicated at 102, 110, 111, 112 and 113 aresubstantially identical in their functions with the corresponding partsshown in FIG. 2.

FIG. 8 shows a further modified driven wheel 203 which comprises a discof synthetic resin on which are embedded outer and inner driven parts210 and 212 with no neutral portion being provided therebetween, saidouter and inner driven parts 210 and 212 being made of magneticsubstance having high magnetic permeability. When the neutral portion iseliminated, the neutral circle is coincident with the inner portions ofthe outer drivcn parts 210 and the outer portions of the inner drivenparts 212.

On the neutral portion being completely eliminated or substantiallyreduced in radial width as in the modifications described just above,the magnetic attractive forces exerted by the magnetic poles on thedriven wheel is increased in magnitude with the result that theself-start ing performance of the driven wheel may be improved.

Referring now to FIG. 9, there is shown another modified driven wheel303 comprising a disc 303a of gear wheel type having therearound aplurality of circumferentially spaced first driven parts 310, and a disc303b of gear wheel type having therearound a plurality ofcircumferentially spaced second driven parts 311, said discs 303a and303b being equal in diameter and superposed one on the other in such amanner that the first driven parts 310 are staggered in relation to thesecond driven parts 311. The discs 303a and 3031) are spaced or notdepending on whether a neutral portion is desired between the two setsof driven parts. In either event the neutral circle is between thediscs. A magnetic pole unit 309 used in cooperation with this drivenwheel 303 is caused to oscillate in the axial direction of the traverseshaft 302 on which discs 303a and 303b are fixed. Components indicatedat 306, 307 and 308 in FIG. 9 are substantially identical in theirfunctions with the counter parts shown in FIGS. 1 and 2.

In a magnetic pole unit having four or five magnetic poles, the magneticpoles should be arranged in such a manner that at least one pitch amongpitches provided between any adjacent magnetic poles is somewhat largerthan an integer times the pitch P provided between the driven partswhile at least one other pitch between adjacent magnetic poles issomewhat smaller than an integer times said pitch P.

While there have been described what are at present considered to be thepreferred embodiments of this invention, it will be obvious to thoseskilled in the art that various changes and modifications may be made.

What we claim and desire to secure by Letters Patent 15:

1. Magnetic driving mechanism comprising a driven wheel having at itsperiphery a first set and a second set of magnetic driven parts disposedrespectively on opposite sides of a magnetically neutral circle, themagnetic driven parts of each said set being spaced circumferentiallyfrom one another and the magnetic driven parts of said second set beingstaggered relative to the magnetic driven parts of said first set, atleast one magnetic pole driving unit having at least three magneticpoles located in opposed relation to said magnetic driven parts, andexciting means for oscillating said magnetic pole driving units in adirection across said magnetically neutral circle to apply rotatingenergy alternately to said two sets of magnetic driven parts, one pitchbetween two of the poles of said driving units being greater than aninteger times the pitch of said driven parts measured along said neutralcircle and another pitch between two of the poles of said driving unitbeing less than an integer times said pitch of said driven parts, thesum total of rotating energy exerted on said magnetic driven parts bysaid magnetic pole driving unit at a time when said driving unit is atone of its amplitude positions being larger than the sum total ofrotating energy exerted on said magnetic driven parts by said magneticpole driving unit at a time when said driving unit is at its oppositeamplitude position, whereby said driven wheel is self starting androtates unidirectionally.

2. Magnetic driving mechanism according to claim 1, in which said twosets of magnetic parts comprise an outer set of said magnetic parts atthe periphery of said driven wheel and an inner set of said magneticparts disposed radially inwardly of said outer set, said driving unitoscillating radially of said Wheel.

3. Magnetic driving mechanism according to claim 2, in which there aretwo said magnetic pole driving units disposed on opposite sides of saidwheel and facing each other.

4. Magnetic driving mechanism according to claim 2, in which said drivenwheel comprises a disc of magnetically permeable material, said magneticparts of said outer set being spaced by notches in the periphery of saiddisc and said magnetic parts of said second set being spaced byapertures in said disc.

5. Magnetic driving mechanism according to claim 2, in which said drivenwheel comprises a disc of non-mag- 8 netic material and said magneticdriven parts comprise spaced portions of magnetically permeable materialset in said disc.

6. Magnetic driving mechanism according to claim 5, in which said discis formed of synthetic resin material.

7. Magnetic driving mechanism according to claim 1, in which said drivenwheel comprises two discs fixed on a common shaft, sad first set ofmagnetic driven parts comprising spaced teeth on one said disc and saidsecond set of magnetic driven parts comprising spaced teeth on the othersaid disc, said magnetic poled driving unit being oscillated in adirection parallel to the axis of said discs. 8. Magnetic drivingmechanism according to claim 1, in which one said pitch of the poles ofsaid magnetic pole driving unit is from 1.1 to 1.2 times said pitch ofsaid driven parts and another said pitch of said magnetic pole drivingunit is from 0.8 to 0.9 times said pitch of said driven parts.

9. Magnetic driving mechanism according to claim 1, further comprisingdamper means connected with said driven wheel to smooth the rotation ofsaid wheel.

10. Magnetic driving mechanism according to claim 1, in which said meansfor oscillating said magnetic pole driving unit comprises a solenoid andmeans for periodically exciting said solenoid.

11. Magnetic driving mechanism according to claim 1, in which each ofsaid magnetic driven parts is symmetrical with respect to a radius ofsaid driven wheel bisecting said driven part.

References Cited UNITED STATES PATENTS 2,913,905 11/1959 Clifford 74-1.52,946,183 7/1960 Clifiord 58116 3,148,497 9/1964 Clifford et a1. 31021 X3,171,991 3/1965 Baumer 3102l DONOVAN F. DUGGAN, Primary Examiner U.S.Cl. X.R.

